Yagi-Uda Array Research Articles

Highly-efficient tunable dipole-driven Yagi–Uda antenna with end-fire radiation for terahertz application

This paper presents a highly efficient tunable dipole antenna with omnidirectional radiation. The main radiator of the hybrid dipole is designed using a perfect electric conductor, whereas tunability has been achieved using graphene strips in the antenna’s proximity. The dipole antenna resonates at 1.3785 THz and provides a bandwidth (BW) of 8.58% for the graphene’s chemical potential (μc) equal to 0.6 eV. The peak gain and total efficiency (ηTotal) are 1.46 dBi and 83.13%, respectively. The proposed dipole provides tunability from 1.32 to 1.411 THz by varying μc from 0.4 to 0.7 eV. Further, a compact dipole-driven tunable Yagi–Uda antenna has been designed with end-fire radiation. The proposed Yagi–Uda antenna has a size of only 90 μm × 60 μm, i.e., 0.61λg×0.38λg, where λg is the guided wavelength calculated at 1.3631 THz and provides tunability from 1.328 to 1.5 THz. The peak gain, front-to-back ratio (FBR) and ηTotal at 1.3631 THz for the μc = 0.6 eV are found to be 4.93 dBi, 17.3 dB, and 63.36%, respectively. A practical parallel plate DC biasing configuration with a common ground plane has also been proposed to independently tune the μc of each element in the passive Yagi–Uda array. The proposed Yagi antenna provides reasonable gain and FBR to cater for high propagation loss in the terahertz regime.

On the Effects of Driven Element L/D Ratio and Length in VHF-SHF Yagi-Uda Arrays

While the Yagi-Uda array has been studied for decades, one issue appears to have received less attention than perhaps it should, namely, the effects on performance of the array’s driven element length and its length-to-diameter ratio. This paper looks at that question. It shows that decreasing the L/D ratio increases impedance bandwidth, but it may shift the IBW band sufficiently far from the design frequency that other parameters such as gain and front-to-back ratio probably are adversely affected. It also shows that array performance is not relatively independent of element diameters. This paper also investigates the effect of lengthening the driven element, which can substantially improve IBW. Several iterations of a 3-element prototype and improved arrays are modeled with the Method of Moments and discussed in detail. A five step design procedure is recommended and applied to a Genetic Algorithm-optimized 3-element Yagi at 146 MHz. This array exhibits excellent performance in terms of gain, front-to-back ratio, and especially impedance bandwidth (nearly 14% for voltage standing wave ratio ≤ 2:1 with two frequencies at which 50 ? is almost perfectly matched). While the analysis and recommended design steps are applied to cylindrical array elements, which commonly are aluminum tubing for stand-alone VHF-SHF Yagis, they can be applied to other element geometries as well using equivalent cylindrical radii, for example, Printed Circuit Board traces for planar arrays. One consequence of lengthening the driven element while reducing its L/D ratio is that some reactance is introduced at the array feedpoint which must be tuned out, and two approaches for doing so are suggested.

A Magnetic Yagi-Uda Antenna With Vertically Polarized Endfire Radiation in Millimeter-Wave Band Applying Higher Order Mode

A magnetic Yagi-Uda antenna applying higher order mode in millimeter-wave (mm-Wave) band with vertically polarized endfire radiation is proposed in this article. Surface wave mode analysis is applied to spot TE mode for magnetic Yagi-Uda antenna in contrast to TM mode for electric Yagi-Uda antenna. A modified structure evolved from conventional U-shaped cavity is used to address the reversed current issue for higher order mode, which exhibits a more uniform phase distribution at the Yagi-Uda array end. Then, a composite end-feeding structure with reflector integrated is further introduced to minimize its parasitic effects for practical antenna design in mm-Wave band. To validate the design, a prototype with a size of 2.7 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{\mathbf {0}}\times1.25\lambda _{\mathbf {0}}\times0.088\lambda _{\mathbf {0}}$ </tex-math></inline-formula> is fabricated and tested. It can achieve anendfiregain of 8–11 dBi within 24–26 GHz with –10 dB impedance band covering an even wider frequency range. The measured front-to-back ratio (FBR) is larger than 16.1 dB. Vertically polarized radiation is realized with cross-polarization level lower than –20 dB atendfiredirection.

Beam steered graphene-based Yagi-Uda array antenna with a transverse magnetic to hybrid mode conversion approach.

This work presents the existence of the mode conversion technique in a graphene-based Yagi-Uda array antenna. It comprises four arrays whose strands are placed on a silicon dioxide substrate, and are eventually connected with the graphene ring. All four driven elements of the Yagi-Uda array antenna are excited through the 50Ω silver nanostrip feedline. The proposed antenna offers mode conversion due to variation of the chemical potential of graphene. It controls conversion of the TM32δ to HEM21δ mode of the antenna. This is attributed to the change in the biasing voltage of graphene. This in turn shifts the radiation pattern from the end-fire to the broadside direction, which effectively confirms the beam reconfigurability. This antenna provides a high directivity of 12.21 dBi at 4.55 THz center frequency. The proposed antenna is designed and analyzed by using CST Microwave Studio, which is based on the finite difference time domain scheme. The beam steered graphene-based antenna has been utilized for several terahertz communication systems.

Analysis and Design of an X-Band Reflectarray Antenna for Remote Sensing Satellite System.

This paper presents the analysis and design of an X-band reflectarray. The proposed antenna can be used for a medium Earth orbit (MEO) remote sensing satellite system in the 8.5 GHz band. To obtain a nearly constant response along the coverage area of this satellite system, the proposed antenna was designed with a flat-top radiation pattern with a beam width of around 29° for the required MEO system. In addition, broadside pencil beam and tilted pencil beam reflectarrays were also investigated. The feeding element of the proposed reflectarray antennas is a Yagi–Uda array. The amplitude and phase distribution of the fields due to the feeding element on the aperture of the reflectarray antenna are obtained directly by numerical simulation without introducing any approximation. The required phase distribution along the aperture of the reflectarray to obtain the required flat-top radiation pattern is obtained using the genetic algorithm (GA) optimization method. The reflecting elements of the reflectarray are composed of stacked circular patches. This stacked configuration was found to be appropriate for obtaining a wide range of reflection phase shift, which is required to implement the required phase distribution on the reflectarray aperture. The antenna was fabricated and measured for verification.

FDTD Computation of Space/Time Integrated Electromagnetic Lagrangian: New Insights Into Design of Mutually Coupled Antennas

In this paper, we develop a formalism based on electromagnetic Lagrangian which provides new insights about the near-field reactive energy density around generic antennas for arbitrary spatio-temporal excitation signals. Using electric and magnetic fields calculated via FDTD technique and interpolation routines,we compute the EM Lagrangian density around antennas (thin-wire dipoles, Yagi-Uda Arrays and planar UWB Monopoles). Spatial maps of time-integrated EM Lagrangian density sheds light onto the capacitive/inductive nature of reactive energy density distribution around antennas and highlight its inherent connection with inter-element mutual coupling. Furthermore, we demonstrate that by minimizing the temporal fluctuations of spatially integrated EM Lagrangian density, it is possible to design MIMO antennas with wide impedance bandwidth and low mutual coupling.

Graphene load for harmonic rejection and increasing the bandwidth in Quasi Yagi–Uda array THz antenna for the 6G wireless communication

The THz array antenna is necessary for many applications such as the 6G satellite communication for the next generation of cell phone services. In this type of antenna increasing the bandwidth and harmonic rejection is vital. In this paper, a novel substrate integrated waveguide (SIW) Quasi Yagi–Uda antenna is suggested with a high Q-factor of 573 for 0.482 THz, and the photonic band-gap structure is also added for amending the antenna Q-factor and reduces the side-lobe level. Basic studies show the effect of SIW formation and PBG on the Q-factor and gain of this antenna. However, arraying and adding a power divider can impact the antenna return loss and increasing the harmonic or resonance in other frequencies which is not interesting in real antennas. Therefore, a THz filter based on the graphene load is added between the power divider and the array antenna to reduce the return loss in harmonic and increasing the bandwidth of the antenna to 15.2 % and the total gain of the antenna is 9.07 dB with a directive pattern and side-lobe level of −5 dB. As a result, the graphene load in the power dividers can be used for omitting unwilling harmonic in the array structure.

Six-Element Yagi Array Designs Using Central Force Optimization with Pseudo Random Negative Gravity

A six-element Yagi-Uda array is optimally designed using Central Force Optimization (CFO) with a small amount of pseudo randomly injected negative gravity. CFO is a simple, deterministic metaheuristic analogizing gravitational kinematics (motion of masses under the influence of gravity). It has been very effective in addressing a wide range of antenna and other problems and normally employs only positive gravity. With positive gravity the six element CFO-designed Yagi array described here exhibits excellent performance with respect to the objectives of impedance bandwidth and forward gain. This paper addresses the question of what happens when a small amount of negative gravity is injected into the CFO algorithm. Does doing so have any effect, beneficial, negative or neutral? In this particular case negative gravity improves CFO’s exploration and creates a region of optimality containing many designs that perform about as well as or better than the array discovered with only positive gravity. Without some negative gravity these array configurations are overlooked. This Yagi-Uda array design example suggests that antennas optimized or designed using deterministic CFO may well benefit by including a small amount of negative gravity, and that the negative gravity approach merits further study.

Central Force Optimization with Gravity &amp;lt; 0, Elitism, and Dynamic Threshold Optimization: An Antenna Application, 6-Element Yagi-Uda Arrays

This paper investigates the effect of adding three extensions to Central Force Optimization when it is used as the Global Search and Optimization method for the design and optimization of 6-elementYagi-Uda arrays. Those extensions are Negative Gravity, Elitism, and Dynamic Threshold Optimization. The basic CFO heuristic does not include any of these, but adding them substantially improves the algorithm’s performance. This paper extends the work reported in a previous paper that considered only negative gravity and which showed a significant performance improvement over a range of optimized arrays. Still better results are obtained by adding to the mix Elitism and DTO. An overall improvement in best fitness of 19.16% is achieved by doing so. While the work reported here was limited to the design/optimization of 6- element Yagis, the reasonable inference based on these data is that any antenna design/optimization problem, indeed any Global Search and Optimization problem, antenna or not, utilizing Central Force Optimization as the Global Search and Optimization engine will benefit by including all three extensions, probably substantially.

Wide Dynamic Range, Angle-Sensing, Long-Wave Infrared Detector Using Nano-Antenna Arrays

We present a new technique for designing angle-sensing, long-wave infrared (LWIR) detectors. Angle detection in the proposed detector is achieved by measuring the ratio of the absorbed power in two closely-spaced, directive infrared antennas. Each directive LWIR antenna is in the form of a three-element Yagi-Uda array sharing a common reflector element with its neighbor. The structure of each antenna is optimized to act both as the collector of the infrared energy from the desired direction and as a distributed bolometer that senses the received radiation. The resistivity of each bolometer-antenna changes as a function of the absorbed power by the antenna. This change of resistance is sensed by biasing each antenna with a constant DC voltage and measuring the change of current passing through the antenna. Following this approach, by measuring the ratio of the resistance change in the two antennas, the angle of arrival of the LWIR signal can be determined. We present the design, fabrication, and measurement results of an angle-sensing detector optimized to operate at the wavelength of λ = 10.6 μm. The proposed detector has subwavelength dimensions occupying an aperture having dimensions of approximately 0.6 λ0 × 0.4λ0. The response of the detector was measured and shows the angle sensing dynamic range of 22 dB within the field of view of ±60°.

Design and Fabrication of Plasma Yagi–Uda Array Antenna With Beamforming

In this paper, the design and implementation of a plasma antenna array using Yagi–Uda reflectors with beamforming is discussed. The structure consists of the circular array of plasma tubes enclosed a unipolar L-band monopole antenna. Beamforming is possible using stimulated plasma tubes. The combination of the above structure with plasma excitation controller provides smart beamforming and uses of the Yagi–Uda structure increases gain compared to previous models. An experimental model in the L-band is fabricated that shows a good agreement between simulated and measured results.

Compact design of two-elements cubic Yagi-Uda array antenna with high gain

Compact design of two-elements cubic Yagi-Uda array antenna with high gain

Study of THz-Plasmon hybridization of a loop Yagi-Uda absorber

In this article we present a three-dimensional loop Yagi-Uda array for efficient, polarization independent and directional absorption of THz radiation over a narrow frequency range (f0 = 0.657 THz & Q factor = 7.5). Unit cell of the array consists of three vertically stacked gold micro rings separated from each other by 30 µm thick SU-8 layers. The proposed array also exhibits a filtering response in its transmittance spectrum. The characteristics are explained by plasmon hybridization method. The transmission, reflection and absorption spectra of the structure are measured and they show a good agreement with corresponding simulated results.

Method of Moment Determination of Current Distribution on Elements of Yagi-Uda Array

Presented in this paper is the numerical solution to the current distributions on two forms of Yagi-Uda antenna designs. One form consists of twelve elements while the other consists of fourteen elements. Employing method of moments technique in which the unknown current is expanded in terms of known expansion function and complex coefficients which are to be determined. It is demonstrated that, when the integral equation that expresses tangential component of an impressed field in terms of induced current on the elements of Yagi-Uda array is reduced into matrix form, the current distribution of interest becomes known. The profiles for the current distributions on elements of those arrays represented in graphical forms reveal that, the currents are symmetrical about the length of the element in each case. It is found that the highest magnitude of the current exists on the driven element. Furthermore, the characteristic profiles of the currents on elements of those arrays exhibit sinusoidal type of waveform and are largely similar when the frequencies of operation are 200MHz and 665MHz, respectively.

Temperature-driven switchable-beam Yagi-Uda antenna using VO2 semiconductor-metal phase transitions

In this study we propose and analyze a temperature driven switchable-beam vertically polarized directional antenna for micro/nano scale optical communications. Temperature enabled phase transitions of a thin layer of vanadium dioxide reshape the beam of a Yagi-Uda antenna by changing the directionality of the radiation pattern and altering the emission rate. The role of each antenna element in the Yagi-Uda array's emission is demonstrated at different temperatures by comparing the amplitudes and phases of induced currents in the elements. Thus a substantial directional gain switching is shown using resonance damping manipulation of antenna elements.

Performance evaluation of two popular antennas designed using a Bacteria Foraging Algorithm

Two popular antennas such as the Yagi-Uda Array (YUA) and the Log Periodic Dipole Array (LPDA) with the same number of dipole elements are optimally designed using Bacteria Foraging Algorithm (BFA). BFA being one of the successful optimization algorithms, used to optimize many design parameters of these two antennas to get a number of desired performance parameters. A YUA is designed here, mainly to realize high directivity, input-impedance (Zin) close to 50Ω, high Front To Back Ratio (FTBR), high Front-to-maximum-Side-Lobe-Level (FSLL), low Half Power Beam Width (HPBW), and appreciable bandwidth, whereas a LPDA is designed here, mainly to achieve high bandwidth, average Zin close to 50Ω, high average FTBR, high average FSLL, low average HPBW, and appreciable average directivity. The successful design approaches, application and comparative study of these two antennas presented here can also be extended to other antennas.

Stacked Yagi-Uda Array for 2.45-GHz Wireless Energy Harvesting

Wireless energy harvesting is currently a popular topic in radiofrequency (RF) engineering. Electromagnetic (EM) energy coming from different kinds of sources has to be collected by the harvester and efficiently converted into dc power. Practical applications include wireless charging systems and dc powering of RF identification (RFID) chips. Space applications were also investigated. Therefore, the third Wireless Energy Harvesting Student Design Competition was organized during the 2014 IEEE Microwave Theory and Techniques Society International Microwave Symposium (IMS2014) in Tampa, Florida.

Scalable RF Energy Harvesting

This paper discusses harvesting of low-power density incident plane waves for electronic devices in environments where it is difficult or impossible to change batteries and where the exact locations of the energy sources are not known. As the incident power densities vary over time and space, distributed arrays of antennas with optimized power-management circuits are introduced to increase harvested power and efficiency. Scaling in array size, power, dc load, frequency, and gain is discussed through three example arrays: a dual industrial-scientific-medical band Yagi-Uda array with a low-power startup circuit; a narrowband 1.96-GHz dual-polarized patch rectenna array with a reconfigurable dc output network designed for harvesting base-station power; and a broadband dual-polarized 2-18-GHz array with multi-tone performance. The efficiency of rectification and power management is investigated for incident power densities in the 1-100-μW/cm2 range.

Analysis, Design and Realization of a Near-Field Focused RF Power Transfer System

This paper reports the analysis, design, prototyping and first measurement results of a linear array antenna consisting of Yagi-Uda elements, rotated and phased for focusing RF power in the near-field of the antenna. By employing Near Field Focusing more power may be transmitted before the EIRP limit is reached due to the inherent far-field difusing. A design based on four Yagi-Uda array elements is able to produce an average power density of 21.04dBm/m2 at 2.45GHz in a box of 10×10×10cm3 located 1m from the linear array face. The design has been verified through comparison with full-wave electromagnetic simulations. First measurements on a realized prototype confirm the functioning of the array.

Circular Beam-Steering Reconfigurable Antenna With Liquid Metal Parasitics

A novel antenna reconfiguration mechanism based on the displacement of liquid metal sections is presented. The liquid nature of the moving parts of the antenna helps avoid the main disadvantage of mechanically-actuated reconfigurable antennas which is the mechanical failure of their solid parts due to material fatigue, creep or wear. Furthermore, the displacement of liquid elements can be more effectively performed than in the case of solid materials by applying precise microfluidic techniques such as continuous-flow pumping or electrowetting. The reconfiguration mechanism is demonstrated through the design, fabrication and measurement of a radiation pattern reconfigurable antenna. This antenna operates at 1800 MHz with 4.0% bandwidth and is capable of performing beam-steering over a 360° range with fine tuning. The antenna is a novel circular Yagi-Uda array, where the movable parasitic director and reflector elements are implemented by liquid metal mercury (Hg). The parasitics are placed and rotated in a circular microfluidic channel around the driven element by means of a flow generated and controlled by a piezoelectric micropump. The measured results demonstrate good performance and the applicability of the microfluidic system.